U.S. patent number 6,806,320 [Application Number 10/295,810] was granted by the patent office on 2004-10-19 for block copolymer melt-processable compositions, methods of their preparation, and articles therefrom.
This patent grant is currently assigned to 3M Innovative Properties Company. Invention is credited to Francois C. D'Haese, Albert I. Everaerts, Ashish K. Khandpur, JingJing Ma, Lang N. Nguyen, Jianhui Xia.
United States Patent |
6,806,320 |
Everaerts , et al. |
October 19, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Block copolymer melt-processable compositions, methods of their
preparation, and articles therefrom
Abstract
Described are melt-processable block copolymers and
compositions, embodiments of which may be useful in applications
such as pressure sensitive adhesive (PSA) or heat-activatable
adhesive, comprising polymeric end block and polymeric B block,
wherein end block comprises copolymer and the B block comprises
homopolymer or copolymer.
Inventors: |
Everaerts; Albert I. (Oakdale,
MN), Ma; JingJing (Woodbury, MN), Khandpur; Ashish K.
(Lake Elmo, MN), D'Haese; Francois C. (Wichelen,
BE), Xia; Jianhui (Woodbury, MN), Nguyen; Lang
N. (St. Paul, MN) |
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
|
Family
ID: |
32297306 |
Appl.
No.: |
10/295,810 |
Filed: |
November 15, 2002 |
Current U.S.
Class: |
525/330.3;
525/191; 525/301; 525/85; 525/80; 525/78; 525/75; 525/299; 525/222;
525/221; 525/227 |
Current CPC
Class: |
C08F
293/005 (20130101); C08F 297/026 (20130101); C08L
53/00 (20130101); C09J 153/00 (20130101); C08L
53/00 (20130101); C09J 153/00 (20130101); C08L
2666/02 (20130101); C08L 2666/02 (20130101); C08L
2666/02 (20130101) |
Current International
Class: |
C09J
153/00 (20060101); C08F 297/00 (20060101); C08F
293/00 (20060101); C08F 297/02 (20060101); C08L
53/00 (20060101); C08F 020/10 (); C08L
031/02 () |
Field of
Search: |
;525/330.3,221,222,227,299,301,75,78,80,85,191 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 349 270 |
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Aug 1994 |
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EP |
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0 921 170 |
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Jun 1999 |
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EP |
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1 094 086 |
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Apr 2001 |
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EP |
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1 234 864 |
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Aug 2002 |
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EP |
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9-324165 |
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Dec 1997 |
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JP |
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10-8011 |
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Jan 1998 |
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JP |
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10-8012 |
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Jan 1998 |
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JP |
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10-8013 |
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Jan 1998 |
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JP |
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10-25459 |
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Jan 1998 |
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JP |
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10-25460 |
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Jan 1998 |
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JP |
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10-30078 |
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Feb 1998 |
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JP |
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WO 97/18247 |
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May 1997 |
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WO |
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WO 00/39233 |
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Jul 2000 |
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WO |
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WO 01/60912 |
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Aug 2001 |
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WO |
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Other References
ASTM D3330-90, Standard Test Methods for Peel Adhesion of
Pressure-Sensitive Tape at 180.degree. Angle. .
ASTM 3654-88, Standard Test Method for Holding power of
Pressure-Sensitive Tapes..
|
Primary Examiner: Seidleck; James J.
Assistant Examiner: Asinovsky; Olga
Attorney, Agent or Firm: Fulton; Lisa P.
Claims
What is claimed is:
1. A method of preparing a poly(meth)acrylate block copolymer,
having meltflow temperature in the range from 50.degree. C. to
250.degree. C., the method comprising: reacting at least one low
glass transition temperature polymeric block and at least one high
glass transition temperature copolymeric end block comprising first
monomeric units and second monomeric units to form the block
copolymer, wherein the low glass transition temperature polymeric
block has a glass transition temperature of less than about
20.degree. C., and the high glass transition temperature
copolymeric end block has a glass transition temperature of at
least about 20.degree. C., and selecting the second monomeric units
to increase or decrease meltflow temperature of the block copolymer
compared to a block copolymer that is otherwise similar but does
not contain the second monomeric units, wherein at least one of the
low glass transition temperature polymeric block and the high glass
transition temperature copolymeric end block is derived from one or
more (meth)acrylate monomer.
2. The method of claim 1 wherein the block copolymer has a cohesive
strength of at least 5,000 minutes measured according to ASTM D
3654.
3. The method of claim 1 comprising selecting the second monomeric
units to decrease meltflow temperature of the block copolymer
compared to a block copolymer that is otherwise similar but does
not contain the second monomeric units, wherein the block copolymer
has a cohesive strength of at least 10,000 minutes measured
according to ASTM D 3654.
4. The method of claim 1 wherein the copolymer comprises high glass
transition temperature copolymeric end block having a glass
transition temperature of the copolymeric block between 20.degree.
C. to 200.degree. C.
5. The method of claim 1 comprising selecting the second monomeric
units to desirably increase meltflow temperature of the block
copolymer compared to a block copolymer that is otherwise similar
but does not contain the second monomeric units, wherein the block
copolymer has a cohesive strength of at least 10,000 minutes
measured according to ASTM D 3654.
6. The method of claim 5 wherein the copolymer comprises
copolymeric end blocks having a glass transition temperature of
from 20.degree. C. to 200.degree. C.
7. The method of claim 5 wherein the copolymer comprises
copolymeric end blocks having a glass transition temperature of the
copolymeric block from 100.degree. C. to 200.degree. C.
8. The method of claim 1 wherein end block copolymer comprises
first monomeric units selected from the group consisting of linear
and branched alkyl(meth)acrylates, cycloaliphatic monomeric units,
and aromatic monomeric units, and second monomeric units selected
from the group consisting of cycloaliphatic and aromatic monomeric
units.
9. The method of claim 1 wherein end block copolymer comprises
first monomeric units selected from the group consisting of linear
and branched alkyl(meth)acrylates, and second monomeric units
selected from the group consisting of cycloaliphatic and aromatic
monomeric units.
10. The method of claim 9 wherein the first monomeric unit is
methyl methacrylate, and the second monomeric unit is selected from
the group consisting of benzyl acrylate, benzyl methacrylate,
cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate,
isobornyl methacrylate, phenylacrylate, phenyl methacrylate,
phenethyl acrylate, phenethyl methacrylate, 2-naphthyl acrylate,
2-naphthyl methacrylate, adamantyl acrylate, adamantyl
methacrylate, styrene, alpha-methylstyrene, and t-butylstyrene.
11. The method of claim 8 wherein the method is used to prepare a
pressure sensitive adhesive composition comprising the block
copolymer.
12. The method of claim 11 wherein the pressure sensitive adhesive
composition comprises tackifier.
13. The method of claim 11 further comprising the step of
crosslinking the pressure sensitive adhesive composition.
14. The method of claim 11 wherein the pressure sensitive adhesive
composition comprises 10 to 200 parts by weight tackifier based on
100 parts by weight block copolymer.
15. The method of claim 11 wherein the pressure sensitive adhesive
composition comprises plasticizer.
16. The method of claim 11 wherein the pressure sensitive adhesive
composition comprises tackifier and plasticizer.
17. The method of claim 11 wherein the composition is a pressure
sensitive adhesive having a cohesive strength of at least 2,000
minutes measured according to ASTM D 3654.
18. A melt-processable poly(meth)acrylate block copolymer, the
block copolymer comprising at least one high glass transition
temperature copolymeric end block having a glass transition
temperature of at least about 20.degree. C., and at least one low
glass transition temperature polymeric block having a glass
transition temperature of less than about 20.degree. C., wherein
high glass transition temperature copolymeric end block comprises
first monomeric units and second monomeric units, the second
monomeric units increasing or decreasing meltflow temperature of
the block copolymer compared to a similar block copolymer that does
not contain the second monomeric units, wherein at least one of the
high glass transition temperature copolymeric end block and the low
glass transition temperature polymeric block is derived from one or
more (meth)acrylate monomer, and the meltflow temperature of the
block copolymer is in the range from 50.degree. C. to 250.degree.
C.
19. The block copolymer of claim 18 wherein the second monomeric
unit increases the meltflow temperature of the block copolymer
relative to a similar block copolymer having end blocks of the
homopolymeric first monomeric units.
20. The block copolymer of claim 18 wherein the second monomeric
unit decreases the meltflow temperature of the block copolymer
relative to a similar block copolymer having end blocks of
homopolymeric first monomeric units.
21. The block copolymer of claim 18 wherein the block copolymer is
a pressure sensitive adhesive having a cohesive strength of at
least 2,000 minutes measured according to ASTM D 3654.
22. The block copolymer of claim 18 comprising first monomeric
units selected from the group consisting of linear and branched
alkyl(meth)acrylates, and second monomeric units selected from the
group consisting of cycloaliphatic and aromatic monomeric
units.
23. The block copolymer of claim 18 wherein the first monomeric
unit is methyl methacrylate, and the second monomeric unit is
selected from the group consisting of benzyl acrylate, benzyl
methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate,
isobornyl acrylate, isobornyl methacrylate, phenylacrylate, phenyl
methacrylate, phenethyl acrylate, phenethyl methacrylate,
2-naphthyl acrylate, 2-naphthyl methacrylate, adamantyl acrylate,
adamantyl methacrylate, styrene, alpha-methylstyrene, and
t-butylstyrene.
24. A melt processable, thermoplastic poly(meth)acrylate block
copolymer comprising at least one soft polymeric block having a
glass transition temperature of less than about 20.degree. C., and
at least two hard copolymeric end blocks having a glass transition
temperature of from 20.degree. C. to 200.degree. C. and comprising
first monomeric units selected from the group consisting of linear
and branched alkyl(meth)acrylates, cycloaliphatic monomeric units,
and aromatic monomeric units, and second monomeric units selected
from the group consisting of cycloaliphatic monomeric units,
aromatic monomeric units, and low glass transition temperature
linear or branched alkyl acrylate or alkyl methacrylate monomeric
units, and
wherein the block copolymer has a meltflow temperature in the from
50.degree. C. to 250.degree. C.
25. The copolymer of claim 24 wherein end block copolymer comprises
first monomeric units selected from the group consisting of linear
and branched alkyl(meth)acrylates, and second monomeric units
selected from the group consisting of cycloaliphatic and aromatic
monomeric units.
26. The copolymer of claim 25 wherein the first monomeric unit is
methyl methacrylate, and the second monomeric unit is selected from
the group consisting of benzyl acrylate, benzyl methacrylate,
cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate,
isobornyl methacrylate, phenylacrylate, phenyl methacrylate,
phenethyl acrylate, phenethyl methacrylate, 2-naphthyl acrylate,
2-naphthyl methacrylate, adamantyl acrylate, adamantyl
methacrylate, styrene, alpha-methylstyrene, and t-butylstyrene.
27. A melt processable, thermoplastic block copolymer comprising at
least one soft polymeric block having a glass transition
temperature of less than about 20.degree. C., and at least two hard
copolymeric end blocks having a glass transition temperature of
from 20.degree. C. to 200.degree. C. and comprising first monomeric
units selected from the group consisting of ethylenically
unsaturated polymerizable cycloaliphatic monomeric units, and
second monomeric units selected from the group consisting of
ethylenically unsaturated polymerizable aromatic monomeric units,
and wherein the block copolymer has a meltflow temperature in the
range from 50.degree. C. to 250.degree. C.
Description
FIELD OF THE INVENTION
The present invention relates to block copolymer melt-processable
compositions such as adhesives, pressure sensitive adhesives,
sealants, elastomers, other hot melt processable compositions, to
methods of their preparation, and to articles having a coating of
such a composition applied thereto.
BACKGROUND
Among adhesive chemistries, poly(meth)acrylates (e.g., polymers
derived at least in part from one or more methacrylate monomer or
acrylate monomer) are one of the most prominent. (Meth)acrylates
have evolved as a preferred class of adhesives due to their
durability, permanence of properties over time, and versatility of
adhesion, to name just a few of their benefits.
Traditionally, adhesives such as (meth)acrylates have been provided
in organic solvent for processing, application, or other
incorporation into a larger product. Solvent based adhesives can be
applied to a substrate and the solvent can be removed, leaving
behind the adhesive.
Hot-melt adhesives advantageously reduce or eliminate the use of
organic solvents in adhesives and their processing. Hot-melt
adhesive systems are essentially 100% solid systems. Usually, such
systems contain no more than about 5% organic solvent or water,
more typically no more than about 3% organic solvent or water. Most
preferably, such systems are free of organic solvent and water.
Advantageously, by reducing the use of organic solvents, special
handling concerns associated with the use of organic solvents are
also reduced.
Melt-processable block copolymer materials have been prepared, as
described in PCT International Publication Number WO 00/39233.
These block copolymers are described as generally contemplated to
include homopolymer or copolymer blocks. According to this
publication and other prior art techniques, to provide a block
copolymer with melt-processing capability, the molecular weight of
homopolymer end blocks may be relatively low. The relatively low
molecular weight of the end blocks can still allow for useful and
acceptable cohesive strength, but the ability to use relatively
higher molecular weight end blocks, without losing melt-processing
capabilities, could be advantageous by further improving other
properties of a block copolymer composition such as cohesive
strength.
SUMMARY
Block copolymers contain at least two different polymeric "blocks"
that cause the bulk block copolymer to exhibit desired properties.
(The term "block copolymer" is used herein to describe a block
copolymer on a molecular scale, and also for convenience to
reference a block copolymer-containing composition or "bulk" block
copolymer). Typically, one block, the end block or "A" block, is a
relatively high glass transition temperature polymeric block that
provides structural and cohesive strength within use temperature
ranges. The "B" block or blocks, which may typically constitute the
middle or core of the block copolymer, have a relatively lower
glass transition temperature and provide elastomeric properties.
The chemistry of the B block can also affect properties of the
block copolymer composition including glass transition temperature
and modulus, which relate to tackiness of the composition.
The polymeric blocks interact with each other in a bulk composition
differently at different temperatures, providing useful
temperature-controlled properties. At low temperatures, e.g., use
temperatures, e.g., temperatures below the glass transition
temperature of the end A blocks and above the glass transition
temperature of the B blocks (e.g., for pressure sensitive adhesive
and elastomer compositions, typically below 100.degree. C. and
above -50.degree. C.), the different blocks organize into ordered A
and B phases, or "phase separate," within the bulk block copolymer
composition. For compositions containing less than about 50 weight
% of the A block, typically microdomains of discontinuous A block
are formed within a continuous phase of B block. The A domains
provide rigidity and strength within the lower modulus continuous B
phase, for a desirable combination of properties. At higher
temperatures, e.g., at a temperature greater than the Tg of an A
block, e.g., greater than 100.degree. C. to about 200.degree. C.,
the bulk block copolymer can be melt processed. In a favorably
designed block copolymer, the thermal energy imparted to the bulk
block copolymer at these temperatures is sufficient to disrupt the
ordered multiphase morphology and create disorder within the block
copolymer composition. The disordered composition does not retain
the strength of the ordered microdomains and as a result can flow
and be "melt processed" relatively easily--melt-processable block
copolymer compositions have a viscosity upon melting that allows
the compositions to be melt-processed (e.g., applied to a
substrate). Upon cooling, the composition returns to the ordered,
strengthened, multi-phase morphology.
FIG. 2 illustrates thermal behavior of a block copolymer of Example
1 over a range of temperatures such that the different regions of
block copolymer viscoelastic behavior could be accessed. G'
(storage modulus), G" (loss modulus), and tan .intg. (the ratio
G"/G') are plotted in the figure as a function of temperature.
These dynamic mechanical measurements were conducted using a
rheometer in a shear geometry. At very low temperatures
(<-50.degree. C.), the entire block copolymer is in a glassy
state and the material is predominantly elastic (G'>>G"). A
precipitous drop is observed in G' over a temperature range (ca.
-50.degree. C. to ca. -10.degree. C.) and a peak in tan
.differential. is observed which is associated with the Tg of the B
block. A plateau in G' is observed from ca. 0.degree. C. to ca.
100.degree. C. and is attributed to the entanglements of the B
block polymer chains. Above ca. 100.degree. C., G' starts dropping
sharply due to the onset of flow in the system and as the Tg of the
A block is exceeded. Accordingly, the viscoelastic response is
dominated by G" in this flow region (G">G') and a steep increase
in tan .differential. (=G'/G') is observed. It is in this "flow
region" of the viscoelastic curve that melt processing is often
conducted.
The temperature at which meltflow occurs is referred to herein as
the meltflow temperature. One convenient measurement of meltflow
temperature that can be used for purposes of this description is
that the meltflow temperature of a block copolymer is the
temperature at the intersection of G' and G" in the flow region of
the viscoelastic curve.
FIG. 1 shows a plot of G' versus temperature for a variety of block
copolymers. The meltflow temperature progressively increases in
this case for copolymers identified herein as Examples 1, 2, 3, and
4. The flow region could not be accessed for Example 5, even when
heated to 240.degree. C., and so it would be difficult to hot melt
process this material without causing thermal degradation or
without the use of other processing aids.
Different features of the molecular structures of the A and B
polymers have been found to affect properties of bulk block
copolymers such as tackiness (or non-tackiness), meltflow
temperature, modulus, Tg, and cohesive strength. These features
include the molecular weight of an A block polymer or a B block
polymer and the ratio of the molecular weight of the A block
polymer to the molecular weight of the B block polymer (MW.sub.A
:MW.sub.B). In general, higher molecular weight A blocks increase
cohesive strength of a bulk block copolymer, but will also increase
meltflow temperature (for a given MW.sub.B), which may not be
desired. The ratio of MW.sub.A to MW.sub.B can have a significant
effect on which phase is the continuous phase, the A block or the B
block. This in turn can alter the properties of the block
composition. Preferred block compositions have a continuous B
block, and it can therefore be preferred to keep the ratio of
MW.sub.A to MW.sub.B in a range to maintain the continuous B
block.
Often, it is desirable to control (e.g., increase or decrease) the
meltflow temperature of a block copolymer, while preferably
retaining other desirable properties of the block copolymer. For
instance, meltflow temperature of a block copolymer may be
desirably reduced if degradation of a polymer is an issue (due to
excessive processing temperature) or where a composition is coated
onto a temperature sensitive substrate. At other times, meltflow
temperature may desirably be increased, for example during
co-extrusion of a block copolymer with another material having a
higher meltflow temperature, to better match processing
characteristics like viscosity.
Past methods of adjusting meltflow temperature have involved
adjusting molecular weight of the A and/or B blocks. As described
above, increasing or decreasing molecular weight of the blocks can
affect (increase or decrease, respectively) the meltflow
temperature of the bulk block copolymer. Unfortunately, the
increase or decrease in molecular weight of the blocks will have a
direct corresponding effect on other properties of the bulk block
copolymer such as cohesive strength or elastomeric characteristics,
which can be undesirable. Also unfortunately, the change in block
molecular weight can cause an unintended and undesirable change in
the ratio of MW.sub.A :MW.sub.B, which can further negatively
affect one or more properties of the bulk block copolymer.
According to the invention, meltflow temperature of a block
copolymer can be selectively controlled and adjusted by choosing
the A block to be a copolymer, and by selecting the composition of
the A block copolymer, i.e., the monomeric units that make up the A
block copolymer, to achieve control of the meltflow temperature
while preferably maintaining, at least to a desired extent,
preferably a substantial extent, other desired properties of the
block copolymer.
The invention specifically allows selection and adjustment of
meltflow temperature of a block copolymer by adjusting the level of
compatibility (or miscibility) between polymeric A and B blocks of
a block copolymer, by selecting the composition of copolymeric A
blocks. The composition of the A blocks is selected to include a
first monomeric unit that provides strength and a desired glass
transition temperature, and a second monomeric unit that desirably
alters the meltflow temperature of the block copolymer without
having to also significantly affect MW.sub.A.
The invention can achieve advantageous rheological properties such
as the ability to adjust, i.e., selectively increase or reduce, a
meltflow temperature, while preferably still providing other
desirable properties of a block copolymer such as high cohesive
strength. By selecting the composition of an A block copolymer
instead of or in addition to molecular weight of the A block, to
adjust meltflow temperature, the level of compatibility between A
blocks and B blocks can be selectively adjusted and controlled
(increased or decreased) without requiring a change in MW.sub.A or
the ratio of MW.sub.A to MW.sub.B. Preferably, this can allow
adjustment and control of meltflow temperature without causing the
same degree of negative effects otherwise created by changing,
e.g., increasing, MW.sub.A. Optionally, in preferred embodiments,
the use of copolymeric end block to alter meltflow temperature can
allow the use of relatively higher molecular weight end block
compared to the use of homopolymeric end block, because meltflow
temperature can be maintained based on the composition of the
copolymeric A block, even at higher molecular weights. A higher
molecular weight A block may allow for improved cohesive strength,
while still retaining a desired (e.g., low) meltflow temperature.
Additionally, the molecular weight ratio of the A block copolymer
to the B block polymer does not have to he affected and the B block
can be maintained as the continuous phase.
The invention specifically contemplates block copolymers having at
least one relatively high glass transition temperature copolymeric
end block ("A block") and at least one relatively lower glass
transition temperature polymeric B block, e.g., at the interior of
the block copolymer. The end blocks can be collectively referred to
as "A" blocks, but all A blocks of a block copolymer molecule or
composition do not necessarily have chemically identical or similar
composition, and while compositions of the invention include block
copolymer with copolymeric A blocks, not all A blocks within a
block copolymer or block copolymer composition are required to be
copolymeric. Some may be homopolymers. B blocks may have the same
or different composition and molecular weight, and may be
homopolymeric or copolymeric.
Preferably, the block copolymer composition can comprise at least
one of an (A-B) diblock copolymer, (A-B-A) triblock copolymer, an
--(A-B).sub.n -- multiblock copolymer, an (A-B).sub.n -- star block
copolymer, and may be a combination of two or more of these.
Particularly preferred are linear (A-B-A) triblock and (A-B).sub.n
-- star block structures. In certain embodiments of the invention,
the block copolymer can be a (meth)acrylate block copolymer,
meaning that at least one of the A and B blocks is derived from one
or more (meth)acrylate monomer.
A blocks of a particular copolymer molecule or of a bulk copolymer
composition can be copolymers independently derived from a
monoethylenically unsaturated monomer that as a homopolymer would
have a glass transition temperature (Tg) of greater than about
20.degree. C., preferably about 20.degree. C. to about 200.degree.
C., and more preferably about 50.degree. C. to about 150.degree. C.
The copolymer can be prepared from a first monoethylenically
unsaturated monomer and a second monoethylenically unsaturated
monomer, to comprise respective first and second monomeric units. A
first monomeric unit can be selected to provide the described Tg of
the A block. Certain preferred first monomeric units can be derived
from linear and branched (meth)acrylate monomers such as methyl
methacrylate, from ethylenically unsaturated cycloaliphatic
monomers (e.g., cyclohexyl methacrylate, isobornyl methacrylate, or
others) or styrenes, or from ethylenically unsaturated aromatic
monomers (e.g., aromatic (meth)acrylates). A second monomeric unit
can be selected to adjust melt processing properties of the block
copolymer, preferably without substantially negatively affecting
other desired properties of the bulk block copolymer. Certain
preferred second monomeric units can be derived from polymerizable,
substituted or unsubstituted, ethylenically unsaturated aromatic or
cycloalkyl monomers, e.g., vinyl-functional or (meth)acrylate
functional cycloalkyl or aromatic monomers such as styrene,
cyclohexylmethacrylate, isobomylmethacrylate, and the like. Any
useful relative amounts of the first and second monomers can be
used, and additional monomers (e.g., a third or fourth monomer) can
also be included in a copolymeric A block if desired, although, it
can be preferred for simplicity that only a small number of
monomers make up the A block copolymer, e.g., two or three.
According to certain methods of the invention, the copolymeric
composition (optionally in combination with molecular weight) of an
A block copolymer can be selected to control a meltflow temperature
of the block copolymer, preferably while at least maintaining or
perhaps even improving other desired block copolymer, structural
features and their dependent properties, such as MW.sub.A :MW.sub.B
of the block copolymer molecule, or modulus or cohesive strength of
a bulk block copolymer. A first monomeric unit can be identified
which as a homopolymeric A block having molecular weight MW.sub.A,
in a particular block copolymer in combination with specified B
blocks, would produce a block copolymer with certain properties of,
e.g., meltflow temperature, modulus, or cohesive strength.
According to the invention, the homopolymeric A block can be
replaced with a copolymeric A block of the same molecular weight,
that contains that same first monomeric unit in combination with a
second monomeric unit. The copolymeric A block can contain second
monomeric units to desirably affect compatibility between the A and
B blocks, thereby increasing or decreasing the meltflow temperature
of the bulk block copolymer, while preferably not substantially
negatively affecting at least one other property of the block
copolymer such as MW.sub.A :MW.sub.B (and related properties),
cohesive strength, or another important property of the block
copolymer. According to this embodiment of the invention, the type
and amount of second monomer can be selected to desirably increase
or decrease meltflow temperature of the block copolymer compared to
a block copolymer that is otherwise similar (e.g., having other of
the same molecular properties such as MW.sub.A :MW.sub.B and
molecular weight of the A and B blocks) but does not contain the
second monomeric units (i.e., the A block is a homopolymer of the
first monomer). Also, use of copolymeric blocks in a block
copolymer, according to the invention, can allow improvement of a
block copolymer having good meltflow properties but poor adhesive
properties. For example, including a copolymeric A block having a
higher MW.sub.A, in such a copolymer, can improve adhesive
properties while retaining meltflow properties.
Preferred A block copolymers can each have a weight average
molecular weight of less than about 100,000 grams per mole e.g.,
from about 3,000 to about 50,000 grams per mole.
Typically, the B block can be a polymer derived from a
monoethylenically unsaturated monomer, that as a homopolymer has a
glass transition temperature (Tg) of less than about 20.degree. C.,
preferably about -70.degree. C. to about 20.degree. C., and more
preferably -60.degree. C. to about 0.degree. C. Preferably, the
monoethylenically unsaturated monomer can be a (meth)acrylate
monomer. B blocks can have a weight average molecular weight of
about 30,000 to about 500,000 grams per mole, more preferably about
50,000 to about 200,000 grams per mole.
The block copolymer can be useful alone or in combination with
other polymeric or non-polymeric materials, preferably in any of a
variety of melt-processable, e.g., "thermoplastic," polymeric
compositions, such as adhesives, sealants, elastomers, reinforced
rubber, and other polymeric compositions. In one embodiment, the
block copolymer can be used as or included in a melt-processable
adhesive composition, e.g., a pressure sensitive adhesive. Examples
of such adhesive compositions may contain the block copolymer as
the only or essentially the only elastomeric component, e.g., may
consist of or consist essentially of the block copolymer and
optional adhesive composition additives such as a tackifier: e.g.,
100 parts by weight of at least one block copolymer comprising at
least two copolymeric A blocks and at least one homopolymeric or
copolymeric B block, and 10 to 200 parts by weight of at least one
tackifier based on total weight of the block copolymer.
Exemplary adhesive compositions of the invention can be pressure
sensitive adhesive (PSA) compositions. However, the invention also
contemplates other adhesive compositions such as heat-activatable
adhesive compositions, as well as non-adhesive compositions.
Preferred adhesive compositions can be formulated to have a
cohesive strength of at least about 2,000 minutes when measured
according to ASTM D 3654, more preferably a cohesive strength of at
least about 5,000 or 6,000 minutes when measured according to ASTM
D 3654, and even more preferably, at least about 10,000 minutes
when measured according to ASTM D 3654.
Broad formulation latitude is possible in block copolymer
compositions of the invention while maintaining melt-processability
and processing efficiency. For example, adhesives such as PSAs are
obtainable even when elastomeric components in the composition
consist of or consist essentially of the block copolymer. Thus,
blending of more than one elastomeric component is not required to
produce adhesive compositions according to the invention.
An aspect of the invention relates to a method of controlling
meltflow temperature of a poly(meth)acrylate block copolymer, the
meltflow temperature of the block copolymer being in the range from
50.degree. C. to 250.degree. C. The method comprises providing
block copolymer comprising at least one low glass transition
temperature polymeric block and at least one high glass transition
temperature copolymeric end block comprising first monomeric units
and second monomeric units, and selecting the amount and type of
the second monomeric units to selectively increase or decrease
meltflow temperature of the block copolymer compared to a block
copolymer that is otherwise similar but does not contain the second
monomeric units.
Another aspect of the invention relates to a melt-processable
poly(meth)acrylate composition comprising block copolymer. The
block copolymer comprises at least one high glass transition
temperature copolymeric end blocks, and at least one low glass
transition temperature polymeric block. The high glass transition
copolymeric block comprises first monomeric units and second
monomeric units, the second monomeric units increasing or
decreasing meltflow temperature of the block copolymer compared to
a similar block copolymer that does not contain the second
monomeric units, and the meltflow temperature of the block
copolymer is in the range from 50.degree. C. to 250.degree. C.
Still another aspect of the invention relates to a melt
processable, thermoplastic poly(meth)acrylate block copolymer. The
copolymer comprises at least one soft polymeric block, and at least
two hard copolymeric end blocks having a glass transition
temperature of from 20.degree. C. to 200.degree. C. and comprising
first monomeric units selected from the group consisting of linear
and branched alkyl(meth)acrylates, cycloaliphatic monomeric units,
and aromatic monomeric units, and second monomeric units selected
from the group consisting of cycloaliphatic monomeric units,
aromatic monomeric units, and low glass transition temperature
linear or branched alkyl acrylate or alkyl methacrylate monomeric
units. The block copolymer has a meltflow temperature from
50.degree. C. to 250.degree. C.
Another aspect of the invention relates to a melt processable,
thermoplastic block copolymer. The block copolymer comprises at
least one soft polymeric block, and at least two hard copolymeric
end blocks having a glass transition temperature of from 20.degree.
C. to 200.degree. C. and comprising first monomeric units selected
from the group consisting of ethylenically unsaturated
polymerizable cycloaliphatic monomeric units, and second monomeric
units selected from the group consisting of ethylenically
unsaturated polymerizable aromatic monomeric units. The block
copolymer has a meltflow temperature in the range from 50.degree.
C. to 250.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a plot of G' versus temperature.
FIG. 2 illustrates a plot of G', G" and tan delta versus
temperature.
DETAILED DESCRIPTION
The invention relates to block copolymers and melt-processable
compositions that contain block copolymers. The composition may be
an adhesive, such as a pressure sensitive adhesive, or a
non-adhesive, such as a sealant, an elastomer such as a reinforced
rubber, or any other type of adhesive or non-adhesive, elastomeric
or polymeric composition that is desirably melt processable and
useful in an application suitable for melt-processable polymeric
materials.
"Block copolymers" as described herein are polymeric elastomeric
materials in which chemically different blocks or sequences bind
each other in macromolecular chains. Block copolymers of the
invention can be divided into two main classes: linear block
copolymers and branched block copolymers. Examples of linear block
copolymers include diblock ((A-B) structure), triblock ((A-B-A)
structure), and multiblock (--(A-B).sub.n -- structure) copolymers
while an example of branched block copolymer is a star block
copolymer ((A-B).sub.n -- structure). Star block copolymers are
also referred to as radial or palmtree copolymers, as they have a
central point from which branches extend. Block copolymers herein
are to be distinguished from comb-type polymer structures and other
branched copolymers. These other branched structures do not have a
central point from which branches extend.
Compositions of the invention can advantageously be
"thermoplastic," meaning that compositions are able to remain
melt-processable after application and cooling, yet retain
preferred characteristics of a crosslinked polymer (e.g., high
cohesive strength and/or creep resistance). Thus, such embodiments
of compositions of the invention may be repeatedly melt-processed,
while still providing desirable properties such as useful cohesive
strength, tack, Tg, modulus, and other useful and desired
properties of adhesives, sealants, and elastomers, after each
application.
Block Copolymers
Block copolymers of the invention comprise at least a copolymeric A
(or "end") blocks and at least one B block that is internal to the
polymer. Preferred block copolymers of the invention may comprise
at least two copolymeric A (or "end") blocks and at least one B
block that is internal to the polymer. The A blocks in block
copolymer structures represent relatively high glass transition
temperature thermoplastic segments, while the B blocks represent
relatively low glass transition temperature elastomeric segments.
The A and B blocks can be derived from monoethylenically
unsaturated monomers to preferably result in saturated polymeric
backbones that do not require subsequent hydrogenation after
polymerization to become saturated. Preferably, at least one of the
A and B blocks can be derived from one or more (meth)acrylate
monomer. Most preferred, at least the B block is derived from one
or more (meth)acrylate monomer. (Meth)acrylate-derived blocks
contribute to preferred properties (e.g., durability, permanence of
properties over time, and versatility of adhesion) in the block
copolymer composition.
The block copolymer, at use temperatures, preferably has an ordered
multiphase morphology. The A blocks are more rigid (i.e., they have
a higher shear modulus and glass transition temperature) than the B
blocks. Typically, the A blocks provide discrete reinforcing
microdomains within an over whelming continuous phase formed from
less rigid B blocks. Generally, the copolymeric A blocks can be
selected such that their solubility parameters are sufficiently
different from those of the B blocks to cause the appropriate phase
separation between the A and B blocks to cohesively reinforce the
elastomer at use temperatures. The term "phase separation" as used
herein refers to the presence of distinct reinforcing A block
domains (i.e., microdomains) in a matrix comprised of the softer B
block phase.
Block copolymers designed to be useful with pressure sensitive
adhesive compositions can be formulated to have a glass transition
temperature (Tg) of the B block of less than about 0.degree. C. For
heat-activatable adhesives, the block copolymer can be tailored to
have a Tg of the B block of about 25.degree. C. to about 30.degree.
C. below the desired heat-activation temperature. Heat-activatable
adhesives are well understood generally to not be pressure
sensitive at a reduced (e.g., room) temperature, but to exhibit
pressure sensitive adhesive properties at higher temperatures, so
as to form a bond at higher temperatures which can remain upon
cooling back to the reduced temperature.
The relative amounts of each block of a block copolymer, e.g., as
measured by molecular weight, can be any relative amounts that
provide a useful block copolymer composition. As stated, the ratio
of MW.sub.A :MW.sub.B can relate to properties of the block
copolymer composition such as cohesive strength and modulus. Useful
values of the ratio of MW.sub.A :MW.sub.B will depend on factors
such as the particular type of block copolymer (e.g., star-block,
tri-block, etc.), the particular chemistries of the different
blocks, and whether other ingredients are included in a block
copolymer composition. Generally, useful relative amounts of A
block to B block can be amounts that provide the desired
morphological structure of the block copolymer composition,
including an ordered multiphase composition having discontinuous A
block phase in a continuous B block phase at use temperatures and a
melt processable morphology at processing temperatures, especially
in a range from 50.degree. C. to 250.degree. C. In addition to
these morphologies, the relative amounts of A and B block polymers
should provide useful properties such as cohesive strength,
modulus, etc. The relative amounts of A and B blocks in any
particular block copolymer will depend on many factors such as the
compositions of each block and the desired properties of the block
copolymer composition. Exemplary ranges for adhesives and
elastomers may be in the range from about 5 to 45 parts by weight A
block per 55 to 95 parts by weight B block, but it is understood
that relative amounts outside of these ranges may also be
useful.
A Blocks
Generally, A blocks are copolymeric, preferably thermoplastic
(i.e., they soften when exposed to heat and return to their
original condition when cooled below their glass transition
temperature) end blocks. The A blocks of preferred block copolymers
can be derived from two or more polymerizable unsaturated monomers,
at least one of which monomers (e.g., the monomer present in the
greatest amount), if separately formed to a homopolymer, would have
a glass transition temperature (Tg) greater than about 20.degree.
C., preferably from about 20.degree. C. to about 200.degree. C.,
more preferably from about 50.degree. to about 180.degree. C., and
even more preferably from 100.degree. C. to about 180.degree.
C.
Copolymers of the A block can be prepared from a first
monoethylenically unsaturated monomer and a second
monoethylenically unsaturated monomer, to comprise respective first
and second monomeric units. The monomeric units may be derived from
suitable polymerizable monomers including (meth)acrylate monomers,
acrylamides, and vinyl unsaturated monomers.
In certain embodiments of the invention, first monomeric units can
be selected as derived from linear and branched (meth)acrylate
monomers, such as methyl methacrylate. Useful (meth)acrylate
monomers have the following general Formula (I): ##STR1##
wherein R.sup.1 is H or CH.sub.3, the latter corresponding to where
the (meth)acrylate monomer is a methacrylate monomer.
R.sup.2 is a hydrocarbon group broadly selected from linear,
branched, aromatic, or cyclic hydrocarbon groups. Preferably, for
first monomeric units R.sup.2 is a linear or branched hydrocarbon
group. The number of carbon atoms in the hydrocarbon group is
preferably about 1 to about 20, and more preferably about 1 to
about 18. When R.sup.2 is a hydrocarbon group, it can also include
heteroatoms (e.g., oxygen or sulfur).
Particularly preferred linear and branched (meth)acrylate monomers
for a first monomeric unit include alkyl (meth)acrylate monomers
which, as homopolymers, exhibit relatively high glass transition
temperatures, including ethyl methacrylate and methyl methacrylate,
especially methyl methacrylate.
Vinyl terminated linear or branched monomers can also be useful as
first monomeric units, e.g., vinyl esters such as vinyl acetate.
Also, a first monomeric unit may be derived from substituted or
non-substituted polymerizable aromatic or cycloalkyl monomers, as
are described in more specific detail below with respect to second
monomeric units. If this is the case, the first and second
monomeric units are still different.
The second monomeric unit can be selected to adjust the melt
processing properties of the block copolymer, specifically
including the meltflow temperature. Certain preferred second
monomeric units can be derived from polymerizable, substituted or
unsubstituted, ethylenically unsaturated aromatic or cycloalkyl
monomers, e.g., vinyl-functional or (meth)acrylate functional
cycloalkyl or aromatic monomers, as well as relatively lower glass
transition temperature linear or branched alkyl acrylate and
methacrylate monomers.
Suitable aromatic or cycloalkyl (meth)acrylate monomers for a
second monomeric unit include benzyl acrylate, benzyl methacrylate,
cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate,
isobornyl methacrylate, phenylacrylate, phenyl methacrylate,
phenethyl acrylate, phenethyl methacrylate, 2-naphthyl acrylate,
and 2-naphthyl methacrylate. Other variations or substituted
versions of these compounds would also be useful, but may not be as
commercially available.
Suitable aromatic or cycloalkyl vinyl-terminated monomers for a
second monomeric unit include, for example, styrenes such as
styrene, alpha-methylstyrene, t-butylstyrene. A particularly
preferred vinyl-terminated monomer is styrene. Other variations or
substituted versions of these compounds would also be useful, but
may not be as commercially available.
Linear or branched alkyl acrylate and methacrylate monomers
suitable for second monomers can include relatively low glass
transition temperature (meth)acrylate monomers, e.g., monomers that
as homopolymers have a Tg in the range of from 50.degree. C. to
-70.degree. C., including ethyl methacrylate, n-butyl acrylate,
n-butyl methacrylate, decyl acrylate, 2-ethoxy ethyl acrylate,
2-ethoxy ethyl methacrylate, isoamyl acrylate, n-hexyl acrylate,
n-hexyl methacrylate, isobutyl acrylate, isodecyl acrylate,
isodecyl methacrylate, isononyl acrylate, 2-ethylhexyl acrylate,
2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl
methacrylate, isotridecyl acrylate, lauryl acrylate, lauryl
methacrylate, 2-methoxy ethyl acrylate, 2-methyl butyl acrylate,
4-methyl-2-pentyl acrylate, n-octyl acrylate, and n-octyl
methacrylate. Also suitable are the n- and t-alkyl acrylamides and
methacrylamides, such as N-octyl acrylamide, t-butyl acrylamide,
and N-isopropylacrylamide.
Particularly preferred monomers for second monomeric units include
styrene, cyclohexylmethyl methacrylate, and isobornyl
methacrylate.
Depending on various factors, any useful relative amounts of first
and second monomers can be used to prepare a copolymeric A block.
The "first," relatively high glass transition temperature monomeric
unit is typically present in an amount to give a desirably high
glass transition temperature, and is typically present as at least
50 molar percent of the monomeric units of the A block. Factors
that will affect the relative amounts of the first and second
monomers in any particular block copolymer may include: the
chemical identities of the first and second monomers, the molecular
weight of the A block, and the chemical composition and molecular
weight of the B block. For example, if the second monomer is a
relatively low glass transition temperature yielding linear or
branched (meth)acrylate, only a relatively small amount can be
included so that a desirably high Tg of the A block is maintained.
If the glass transition temperatures of the first and second
monomers are nearly the same, then either may be used in a very
broad range of relative amounts.
Additional monomers (e.g., a third or fourth monomer) can be
included in a copolymeric A block, although it can be preferred for
simplicity that only a small number of different monomers make up
the A copolymer, e.g., two or three. Examples of other monomers
could be reactive monomers that would allow crosslinking of the
block copolymer. Specific examples may include acrylic acid,
2-hydroxyethyl (meth)acrylate (for chemical crosslinking); and
4-acryloxy-benzophenone (for photo crosslinking).
While it is desired that the copolymeric blocks be relatively pure,
meaning that there are few if any monomeric units in the A block
that were intended to be part of the B block, such accidental
impurity can occur, but by itself is not considered to constitute a
copolymeric A block as described herein.
The A blocks can be of any molecular weight that provides useful
properties such as meltflow temperature, modulus, cohesive
strength, and desired (high or low) tackiness, for a given block
copolymer composition. Preferred molecular weights can provide a
desired combination of these properties. Exemplary molecular
weights can be weight average molecular weights below about 100,000
grams per mole, with a weight average molecular weight of about
3,000 to about 50,000 grams per mole being preferred. These
relatively low molecular weights facilitate melt-processing of
adhesives comprising the block copolymers. Advantageously, the use
of copolymeric A blocks as described herein, instead of
homopolymers, can in certain embodiments of the invention allow for
the use of higher molecular weight copolymeric end blocks (as
opposed to homopolymeric end blocks) while still maintaining
melt-processability in a particular temperature range.
Although this description specifies that block copolymer
compositions of the invention include copolymeric A blocks, a block
copolymer molecule or composition can also include some A blocks
that are homopolymers, if desired.
B Blocks
Generally, the B blocks are elastomeric polymeric blocks, e.g.,
homopolymers or copolymers, derived from monoethylenically
unsaturated monomers. In particular embodiments, the B block can be
derived from monoethylenically unsaturated monomer that as a
homopolymer has a glass transition temperature (Tg) of less than
about 20.degree. C., particularly when the composition can
inherently be a pressure sensitive adhesive block copolymer,
without the need for added plasticizer or tackifier. In other
particular embodiments, B block polymers can be derived from
monoethylenically unsaturated monomers that as homopolymers have a
Tg of about -70.degree. C. to about 20.degree. C., more preferably
from about -60.degree. C. to about 0.degree. C., or from
-60.degree. C. to about -10.degree. C.
When the block copolymer is designed for use as or in a
heat-activatable adhesive, monomer selection for the B block can be
modified accordingly. For example, monomers used to prepare a B
block for use as or in a heat-activatable adhesive can be selected
such that the resulting polymer has a bulk modulus greater than the
Dahlquist criterion. Alternatively, Tg of the B block can be
controlled to provide a resultant block copolymer having a Tg of
about 25.degree. C. to about 30.degree. C. below the desired
heat-activation temperature. Another way of obtaining
heat-activatable adhesives is by adding a large proportion of
tackifiers to the adhesive composition (see below).
Preferred B blocks can be homopolymers and copolymers derived from
one or more monoethylenically unsaturated monomers such as
(meth)acrylate esters of non-tertiary alkyl alcohols, the alkyl
groups of which comprise from about 1 to about 20, preferably about
1 to about 18 carbon atoms, including polar monomers such as
methacrylic acid, itaconic acid, and acrylic acid, N-alkylated or
N,N-dialkylated acrylamides and methacrylamides; hydroxyalkyl
methacrylates and acrylates; and vinyl-terminated monomers (e.g.,
vinyl esters). Preferred B blocks can be derived from at least one
(meth)acrylate monomer.
Useful (meth)acrylate monomers have the following general Formula
(I): ##STR2##
wherein R.sup.1 is H or CH.sub.3, the latter corresponding to where
the (meth)acrylate monomer is a methacrylate monomer. Preferably,
R.sup.1 is H, as acrylates are generally less rigid than their
methacrylate counterparts.
R.sup.2 is a hydrocarbon group broadly selected from linear,
branched, aromatic, or cyclic hydrocarbon groups. Preferably,
R.sup.2 is a linear or branched hydrocarbon group. The number of
carbon atoms in the hydrocarbon group is preferably about 1 to
about 20, and more preferably about 1 to about 18. When R.sup.2 is
a hydrocarbon group, it can also include heteroatoms (e.g., oxygen
or sulfur).
Suitable (meth)acrylate monomers for a B block can include, for
example, n-butyl acrylate, decyl acrylate, 2-ethoxy ethyl acrylate,
2-ethoxy ethyl methacrylate, isoamyl acrylate, n-hexyl acrylate,
n-hexyl methacrylate, isobutyl acrylate, isodecyl acrylate,
isodecyl methacrylate, isononyl acrylate, 2-ethylhexyl acrylate,
2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl
methacrylate, isotridecyl acrylate, lauryl acrylate, lauryl
methacrylate, 2-methoxy ethyl acrylate, 2-methyl butyl acrylate,
4-methyl-2-pentyl acrylate, n-octyl acrylate, and n-octyl
methacrylate, and polar monomers such as acrylic acid, methyl
methacrylate, or other polar monomers as mentioned above.
Typically, such polar monomers can be useful at levels below 40
parts by weight per 100 parts by weight of total monomer used in a
B block, e.g., from 0 to 20 parts by weight polar monomer per 100
parts by weight total B block.
Monomeric units analogous to those desired from (meth)acrylate
monomers that are synthetically undesirable or commercially
unavailable can be provided through trans-alcoholysis (i.e.,
replacement of an alcohol group on the B block by a different
alcohol group) or hydrolysis of a polymerized B block. When the
polymerized B block is hydrolyzed, it can be followed by
esterification. This process may leave some residual acid in the
block copolymer.
The molecular weight of the B block can be such that a continuous
phase is formed in the block copolymer. Preferably, the B blocks
have a weight average molecular weight of about 30,000 to about
500,000 grams per mole and, more preferably, a weight average
molecular weight of about 70,000 to about 200,000 grams per
mole.
Polymerization
Any technique that produces well-controlled block copolymer
structures can be suitable for preparing block copolymers of the
invention. (See, e.g., WO 00/39233, incorporated herein by
reference.) These techniques can include living free radical
polymerization techniques, living anionic polymerization, and group
transfer polymerization. Specific examples of living free radical
polymerization include: atom transfer polymerization, reversible
addition-fragmentation chain transfer polymerization, and
nitroxide-mediated polymerization.
Living anionic polymerization typically leads to more stereoregular
block structures than those blocks polymerized using free radical
polymerization. Stereoregularity (as evidenced by highly
syndiotactic and/or isotactic structures) contributes to block
copolymers having well-controlled block structures and influences
the glass transition temperature of the block. For example,
syndiotactic polymethyl methacrylate (PMMA) synthesized using
living polymerization has a glass transition temperature that is
about 20-25.degree. C. higher than a comparable PMMA synthesized
using conventional free radical polymerization. Stereoregularity is
detectable, for example, using nuclear magnetic resonance
spectroscopy, differential scanning calorimetry, or similar
analytical techniques. Structures with greater than about 75%
stereoregularity are obtainable when using living
polymerization.
Living anionic polymerization is sometimes preferred. However, when
polymerizing at higher temperatures (e.g., greater than about
-40.degree. C.), living free radical polymerization may be
preferred, as living free radical polymerization is typically less
sensitive to high temperature than is living anionic
polymerization.
Preferably, the molecular weight of the block copolymer is
controlled. That is, theoretical molecular weight ranges of the A
and B blocks are obtainable after polymerization. Preferably the
resulting molecular weight is about 0.7 to about 1.5 times the
predicted molecular weight, more preferably about 0.8 to about 1.2
times the predicted molecular weight, and most preferably about 0.9
to about 1.1 times the predicted molecular weight. As such, desired
block copolymer structures can be designed (i.e., theoretically)
and then easily replicated by the selected polymerization
method.
In certain embodiments of the block copolymer, where desired or
useful, polydispersity (as measured, for example, by gel permeation
chromatography) of each block and the overall block copolymer can
be about 2.0 or less, e.g., about 1.7 or less, and even about 1.5
or less. If desired, polydispersity of each block and the overall
block copolymer can be as close to 1.0 as possible.
Also in certain embodiments of the invention, if desired,
boundaries between microdomains comprising the A blocks and the
continuous phase comprising the B blocks can be well-defined (i.e.,
the boundaries are essentially free of tapered structures--those
structures derived from monomers used for both the A and B blocks).
Tapered structures can affect onset of flow (i.e., typically
decrease it), and also can affect cohesive strength.
When using living anionic polymerization to form a block copolymer,
typically the first step of the process involves contacting
monomers of the A block with an initiator in the presence of an
inert diluent to form a living polymer. The inert diluent used in
the polymerization process facilitates heat transfer and adequate
mixing of the initiator and monomer. Any suitable inert diluent may
be used. Typically the inert diluent can be a saturated
hydrocarbon, aromatic hydrocarbon, or ether. Examples of such
diluents include: saturated aliphatic and cycloaliphatic
hydrocarbons, such as hexane, heptane, octane, cyclohexane, and the
like; and aromatic hydrocarbons, such as toluene. In addition,
aliphatic and cyclic ether solvents may be used, such as dimethyl
ether, diethyl ether, and tetrahydrofuran.
When using living anionic polymerization, the living polymer can be
represented by a simplified structure, A-M, where M represents a
Group I metal such as Li, Na and K and A represents the A block.
For example, when a charge of different monomer (B) is then added,
followed by another charge of monomer for the A block, an (A-B-A)
triblock copolymer results. The molecular weight of the polymer
blocks formed is determined by the amounts of initiator and monomer
used. Alternatively, living A-B-M (i.e., a living diblock) can be
coupled using difunctional or multifunctional coupling agents to
form (A-B-A) triblock or (A-B).sub.n -- star block copolymers,
respectively.
Any suitable initiator or combination thereof can be used. Typical
initiators include alkali metal hydrocarbons. For example,
monofunctional initiators are useful initiators in the first step
of the process described above, such as organomonolithium. These
compounds are represented by the structure R-Li where "R" is an
aliphatic, cycloaliphatic or aromatic radical and "Li" is lithium.
Examples include ethyl lithium, n-propyl lithium, iso-propyl
lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium,
n-decyl-lithium, phenyl lithium, 2-naphthyl lithium, 4-butylphenyl
lithium, 4-phenylbutyl lithium, cyclohexyl lithium, and the
like.
Difunctional initiators may also be used. Difunctional initiators
include, for example, 1,1,4,4-tetraphenyl- 1,4-dilithiobutane;
1,1,4,4-tetraphenyl- 1,4-dilithioisobutane; naphthalenelithium;
naphthalenesodium; naphthalenepotassium; homologues thereof;
dilithium initiators (e.g., those prepared by addition reaction of
alkyl lithium with a divinyl compound, for example,
1,3-bis(1-phenylethenyl)benzene; m-diisopropenylbenzene); and the
like.
Co-initiators may also be used. Co-initiators include, for example,
lithium halides (e.g., lithium chloride); alkali metal alkoxides;
oligomeric (or polymeric) ethers or amides, alkali metal
derivatives thereof; and alkyl aluminum compounds.
When living free radical polymerization is used, any suitable
initiator or combination thereof can be used. For a description of
living free radical polymerization and suitable initiators, see PCT
Publication No. WO 97/18,247 (Carnegie Mellon) and PCT Publication
No. WO 98/01,478 (E.I. duPont de Nemours and Co.).
The amount of initiator used during living polymerization usually
affects the molecular weight of the living polymer. If a small
portion of initiator is used with respect to the amount of monomer,
the molecular weight of the living polymer will generally be larger
than if a large portion of initiator is used.
For living anionic polymerization, it is generally advisable to add
the initiator dropwise to the monomer until the persistence of the
characteristic color of the organic anion in the initiator is
observed. Then, the calculated amount of the initiator is added for
the molecular weight desired. The preliminary dropwise addition
serves to destroy contaminants and, thus, permits better control of
the polymerization.
The polymerization temperature will depend on the monomers being
polymerized and the type of polymerization method being used.
Generally, the reaction can be carried out at a temperature ranging
from about -100.degree. C. to about 100.degree. C. Usually the
polymerization temperature is about -80.degree. C. to about
20.degree. C. when using living anionic polymerization and about
20.degree. C. to about 100.degree. C. when using living free
radical polymerization.
In general, the polymerization should be carried out under
controlled conditions to exclude substances that destroy the
initiator, radical, or living anion. Typically, the polymerization
can be carried out in an inert atmosphere, such as nitrogen,
helium, or argon. When living anionic polymerization is used,
anhydrous conditions may be necessary.
Compositions Containing the Block Copolymer
The block copolymer can be used by itself or in combination with
other ingredients to provide any of a variety of useful polymeric
compositions, including sealants, adhesives, elastomers, or other
melt-processable polymeric compositions.
Adhesives of the invention can comprise a major proportion of at
least one block copolymer (more than one block copolymer of the
present invention may be blended together) of the invention with
respect to the total elastomeric components. "Elastomeric
components" are components having the ability to be stretched to at
least twice their original length and to retract very rapidly to
approximately their original length when released. Block copolymers
of the invention do not need to be used in combination with one or
more other adhesive ingredients, but an adhesive composition of the
invention can consist of or consist essentially of block copolymer
of the invention as the only elastomeric component. In certain
preferred embodiments of adhesive compositions, other elastomeric
components are not present at all or are present only in minor
amounts such as less than about 5 parts by weight of the total
adhesive composition.
Particular embodiments of the invention include compositions that
work as pressure sensitive adhesives (PSAs). PSAs are well known to
those of ordinary skill in the art to possess properties including
the following: (1) aggressive and permanent tack, (2) adherence
with no more than finger pressure, (3) sufficient ability to hold
onto an adherend, and (4) sufficient cohesive strength to be
removed cleanly from the adherend.
"Heat-activatable adhesive systems" are another type of
melt-processable composition contemplated by the invention.
Heat-activatable adhesives are substantially nontacky at room
temperature, but become tacky upon heating. Heat-activatable
systems, unlike PSA systems, rely on a combination of pressure and
heat to bond to a surface.
Components of compositions of the invention can advantageously be
selected to provide melt-processable adhesives without sacrificing
cohesive strength of the applied adhesive. Preferred adhesives
according to the invention can have cohesive strengths of at least
about 2,000 minutes, more preferably at least about 6,000 minutes,
and most preferably at least about 10,000 minutes when measured
according to ASTM D 3654. These cohesive strengths are obtainable
even in the absence of chemical crosslinking.
One potential advantage of block copolymers of the invention is
that they have adequate cohesive strength for many applications,
after application, without the need for subsequent curing steps.
Although generally not necessary, additional curing steps may be
used, however, if so desired. Such additional curing steps include
exposing the adhesive to radiation, such as ultraviolet or electron
beam radiation.
Additives
Other ingredients and additives may be combined with the block
copolymer prior to use or application thereof, the type and amount
depending on the desired properties of the block copolymer
composition.
Any suitable additive may be blended into the block copolymer. For
example, to improve melt-processability, A block-compatible resins
may also be used in the compositions. Those of ordinary skill in
the block copolymer art will recognize many suitable additives.
However, solubility parameter differences between blocks in
rubber-based (e.g., polystyrene-polydiene type) block copolymers
are usually different than in copolymers of the present invention
containing blocks derived from monoethylenically unsaturated
monomers, such as (meth)acrylate monomers (i.e., the difference in
solubility parameters between the A and B blocks is typically
smaller than in rubber-based block copolymers). Thus, selective
tackification or plasticization of each block requires different
considerations than when rubber-based block copolymers are used.
Thus, additive selection in the present case is quite different
than when rubber-based block copolymers are used.
Preferably, any additive used, however, is compatible with the B
block of the block copolymer of the invention. An additive is
compatible in a phase (e.g., A block or B block) if it causes a
shift in the glass transition temperature (Tg) of that phase
(assuming that the tackifier and the tackifier-free phase do not
have the same Tg).
Other polymers or non-polymers, or other types of the inventive
block copolymer, may be blended with the block copolymer
composition. However, in certain embodiments of the invention, this
is not necessary. For example, minor amounts of block copolymers
having an (A-B) diblock structure may be present in block
copolymers having a different block structure, e.g., A-B-A.
Alternatively, it may be desirable to add further block copolymer
having an (A-B) diblock structure to a composition containing a
different structure, e.g., A-B-A. The further addition of diblock
copolymer may facilitate melt-processability of a composition
comprising an A-B-A copolymer, as well as increase the level of
tack (depending on the compositions of A and B). Typically, if a
block copolymer having an (A-B) diblock structure is used with an
A-B-A block copolymer, the amount of A-B diblock copolymer can be
up to about 80 parts by weight based on 100 parts by weight of the
A-B-A block copolymer. Preferably at least the A block of such
diblock copolymer is the same chemical composition as the A block
of the A-B-A block copolymer, most preferably both the A and B
blocks are the same chemical composition as the A and B blocks of
the A-B-A block copolymer.
Certain embodiments of the block copolymer of the invention may not
be sufficiently tacky for a desired application, e.g., as a
pressure sensitive adhesive. Thus, it may be useful, if desired, to
add a tackifying resin (i.e., tackifier or combination of them) to
increase a tack. It may be useful to use relatively large
proportions of tackifying resins, if desired. In general,
tackifying resins are less expensive than block copolymers.
Furthermore, large proportions of B block compatible tackifying
resins may also be desirable when formulating to provide
heat-activatable adhesives. Tackifying resins can also facilitate
melt-processability.
Typically, at least one tackifying resin can be selected to be
compatible with the B block, but it may also be partially
compatible with the A block. Preferably, a tackifying resin can be
compatible with the B block and incompatible with the A block.
Solid or liquid tackifiers can be used. Solid tackifiers generally
have a number average molecular weight (Mn) of 10,000 grams per
mole or less and a softening point above about 70.degree. C. Liquid
tackifiers are viscous materials that have a softening point of
about 0.degree. C. to about 70.degree. C.
Suitable tackifying resins include rosins and their derivatives
(e.g., rosin esters); polyterpenes and aromatic-modified
polyterpene resins; coumarone-indene resins; and hydrocarbon
resins, for example, alpha pinene-based resins, beta pinene-based
resins, limonene-based resins, aliphatic hydrocarbon-based resins,
aromatic-modified hydrocarbon-based resins, aromatic hydrocarbon
resins, and dicyclopentadiene-based resins. Non-hydrogenated
tackifying resins are typically more colored and less durable
(i.e., weatherable) than block copolymers of the present invention.
Thus, when appropriate, hydrogenated (either partially or
completely) tackifying resins may also be used. Examples of
hydrogenated tackifying resins include, for example: hydrogenated
rosin esters, hydrogenated rosin acids, hydrogenated aromatic
hydrocarbon resins, hydrogenated aromatic-modified
hydrocarbon-based resins, and hydrogenated aliphatic
hydrocarbon-based resins. Particularly preferred hydrogenated
tackifying resins include hydrogenated rosin esters, hydrogenated
rosin acids, hydrogenated aromatic hydrocarbon resins, and
hydrogenated aromatic-modified hydrocarbon-based resins.
Any useful amount of tackifying resin may be combined with a useful
amount of block copolymer and optionally other ingredients. For
example, tackifying resin can be present in an adhesive composition
in an amount of about 10 to about 200 parts by weight tackifier
based on 100 parts by weight block copolymer. Higher or lower
amounts may be desired, however, especially higher amounts when
formulating heat-activatable adhesives.
Plasticizers may also be used in combination with the block
copolymer. Plasticizers are well known and may include, for
example, hydrocarbon oils (e.g., those that are aromatic,
paraffinic, or naphthenic), hydrocarbon resins, polyterpenes, rosin
esters, phthalates, phosphate esters, dibasic acid esters, fatty
acid esters, polyethers, and combinations thereof. Plasticizers are
optional and may be present in compositions of the invention in any
suitable amount, such as for example, amounts up to about 100 parts
by weight, preferably up to about 50 parts by weight, based on 100
parts by weight of block copolymer. These plasticizers may or may
not be used in combination with the tackifiers described above.
Photocrosslinkers can also be added for optional subsequent curing
by UV-irradiation. Conventional crosslinking agents (physical,
ionic, and chemical crosslinking agents) can also be used in
embodiments of the present invention. Crosslinkers are optional and
may be present in compositions of the invention in any suitable
amount, such as amounts up to about 5 parts by weight based on 100
parts by weight of the total composition.
Other optional additives include, for example, stabilizers (e.g.,
antioxidants or UV-stabilizers), pigments, fillers, medicaments,
and the like. The use of such additives is well known to those of
ordinary skill.
Application of Melt-processable Adhesive Compositions
Preferred block copolymer compositions can be readily applied to a
substrate by melt processing methods. For example, a
melt-processable adhesive can be applied to a sheeting product
(e.g., decorative, reflective, and graphical); borders of, for
example, medical electrodes and drug delivery patches; labelstock;
and tape backings. The substrate can be any suitable type of
material depending on the desired application. Typical substrates
can comprise a nonwoven, woven, foam, paper, polypropylene (e.g.,
biaxially oriented polypropylene (BOPP)), polyethylene, polyester
(e.g., polyethylene terephthalate), or release liner (e.g.,
siliconized liner).
Thus, melt-processable adhesives according to the present invention
can be used to form tape, for example. To form a tape, a
melt-processable adhesive is coated onto at least a portion of a
suitable backing. A release material (e.g., low adhesion backsize)
can be applied to the opposite side of the backing, if desired.
When double-sided tapes are formed, adhesives are coated onto at
least a portion of both sides of the backing.
Melt-processable block copolymer compositions of the invention can
be applied to substrates using methods well known to one of
ordinary skill. For example, the block copolymer and other
components can be blended and applied using for example, one of
spraying, melt-extruding, blowing (e.g., into blown microfibers),
printing (e.g. rotary screen-printing) and foaming techniques to
form adhesive-coated substrates of the present invention.
An adhesive or other block copolymer composition can be formed into
a film or coating by either continuous or batch processes. An
example of a batch process is the placement of a portion of
adhesive between a substrate to which the film or coating is to be
adhered and a surface capable of releasing the adhesive film or
coating to form a composite structure. The composite structure can
then be compressed at a sufficient temperature and pressure to form
an adhesive coating or layer of a desired thickness after cooling.
Alternatively, the adhesive can be compressed between two release
surfaces and cooled to form an adhesive transfer tape useful in
laminating applications.
Continuous forming methods include drawing the melt-processable
block copolymer composition from a film die and subsequently
contacting the drawn adhesive to a moving plastic web or other
suitable substrate. A related continuous method involves extruding
the composition and a coextruded backing material from a film die
and cooling the layered product, e.g., to form an adhesive tape.
Other continuous forming methods involve directly contacting a
block copolymer composition to a rapidly moving plastic web or
other suitable preformed substrate. Using this method, the block
copolymer composition can be applied to the moving preformed web
using a die having flexible die lips, such as a rotary rod die.
After forming by any of these continuous methods, the block
copolymer films or layers can be solidified by quenching using both
direct methods (e.g., chill rolls or water baths) and indirect
methods (e.g., air or gas impingement).
Although coating without using solvent can be preferred, block
copolymer compositions of the invention can optionally be coated
using solvent-based methods. For example, the compositions can be
coated by such methods as knife coating, roll coating, gravure
coating, rod coating, curtain coating, and air knife coating. Any
suitable solvent can be used. Examples of suitable solvents include
ethyl acetate, acetone, methyl ethyl ketone, and combinations
thereof. After coating, the composition can be dried to remove
solvent. The coated composition can be subjected to increased
temperatures, such as those supplied by an oven, to expedite drying
of the adhesive.
The block copolymers, melt-processable adhesives therefrom and
processes herein are exemplified in the following examples. These
examples are merely for illustrative purposes only and are not
meant to be limiting on the scope of the appended claims. All
parts, percentages, ratios, etc. in the examples and the rest of
the specification are by weight unless indicated otherwise.
EXAMPLES
Table of Abbreviations AA Acrylic acid IOA isooctyl acrylate EHA
2-ethylhexyl acrylate NBA n-butyl acrylate PET polyester film of
polyethylene terephthalate having a thickness of 38 micrometers
(1.5 mils) CHMA Cyclohexylmethacrylate MMA Methylmethacrylate IBMA
isobornylmethacrylate TBA tert-butyl acrylate PHR Parts per 100
parts of rubber (block copolymer) F105 Foral 105 rosin ester
tackifying resin commercially available from Hercules, Wilmington,
Delaware F85 Foral 85 rosin ester tackifying resin commercially
available from Hercules, Wilmington, Delaware R1018 Regalrez 1018
hydrocarbon tackifying resin commercially available from Eastman
Chemical, Kingsport, Tennessee SP553 Schenectady SP553 terpene
tackifying resin commercially available from Schenectady
International, Schenectady, NY BLUE X Blueminster X rosin ester
tackifying resin commercially available from Blueminster Ltd.,
Kemsing Sevenoaks, Kent, UK WINGTA Synthetic tackifier commercially
available from Goodyear, CK PLUS Akron, Ohio KRATON Block copolymer
commercially available from Kraton D1107 Polymers, Houston, TX
Test Methods
180.degree. Peel Adhesion
This peel adhesion test is similar to the test method described in
ASTM D 3330-90, substituting a glass or polyethylene (PE) substrate
for the stainless steel substrate described in the test.
Adhesive coatings on polyester film were cut into 1.27 centimeter
by 15 centimeter strips. Each strip was then adhered to a 10
centimeter by 20 centimeter clean, solvent washed glass coupon
using a 2-kilogram roller passed once over the strip. The bonded
assembly dwelled at room temperature for about one minute and was
tested for 180.degree. peel adhesion using an IMASS slip/peel
tester (Model 3M90, commercially available from Instrumentors Inc.,
Strongsville, Ohio) at a rate of 0.3 meters/minute (12
inches/minute) over a five second data collection lime. Two samples
were tested; the reported peel adhesion value is an average of the
peel adhesion value from each of the two samples. Additionally,
samples were allowed to dwell at constant temperature and humidity
conditions for 24 hours and then were tested for 180.degree. peel
adhesion.
Shear Strength
This shear strength test is similar to the test method described in
ASTM D 3654-88.
Adhesive coatings on polyester film were cut into 1.27 centimeter
(0.5 inch) by 15 centimeter (6 inch) strips. Each strip was then
adhered to a stainless steel panel such that a 1.27 centimeter by
1.27 centimeter portion of each strip was in firm contact with the
panel and one end portion of the tape being free. The panel with
coated strip attached was held in a rack such that the panel formed
an angle of 178.degree. with the extended tape free end, which was
tensioned by application of a force of one kilogram applied as a
hanging weight from the free end of the coated strip. The 2.degree.
less than 180.degree. was used to negate any peel forces, thus
ensuring that only shear strength forces were measured, in an
attempt to more accurately determine the holding power of the tape
being tested. The time elapsed for each tape example to separate
from the test panel was recorded as the shear strength. All shear
strength failures (if the adhesive failed at less than 10,000
minutes) reported herein were adhesive failures (i.e. no adhesive
residue was left on the panel) unless otherwise noted. Each test
was terminated at 10,000 minutes, unless the adhesive failed at an
earlier time (as noted).
Quick Stick Test
Quick Stick tests were carried out according to the AFERA 4015 test
method.
Dynamic Mechanical Analysis
Elastomers were tested by Dynamic Mechanical Analysis (DMA) in a
parallel plate rheometer (RDA II, Rheometrics, Inc; Piscataway,
N.J.) while the sample was heated from room temperature to
200.degree. C. at a rate of 2.degree. C./minute, a frequency of 1
radian/second, and a maximum strain of 10% to determine the rubbery
plateau and the "crossover temperature". The crossover temperature
is the highest temperature point where the G' and G" curves
intersect or the highest temperature point where tangent delta
=1.
Examples 1-5
A series of polymers of the ABA block copolymer type were prepared
with an approximate 60/40 ratio of CHMA/MMA in the A blocks and
poly-IOA of about 170,000 molecular weight in the B block (actual
values are shown in Table 1). The preparation of each polymer was
carried out using anionic polymerization techniques in a 3 step
synthesis.
Step 1: Preparation of Poly-t-butylacrylate Macro-initiator
In a glass vessel dried and purged with nitrogen was added THF,
LiCl, naphtalene/.alpha.-methylstyrene and a solution of sec-butyl
lithium in cyclohexane. The solution was cooled to -78.degree. C.
and TBA was added. Polymerization was allowed to proceed for about
one hour at -78.degree. C., so complete conversion of the TBA was
obtained.
Step 2: Preparation of CHMA/MMA-TBA-CHMA/MMA Block Copolymer
To the difunctional polyTBA initiator prepared in Step 1 was added
the CHMA and MMA monomers in the desired ratio. Polymerization was
allowed to proceed for about one hour at -78.degree. C., so all the
monomers were essentially depleted. The reaction was then quenched
with methanol, the polymer precipitated with a 90/10 mixture of
water/methanol and dried under vacuum overnight.
Step 3: Conversion to CHMA/MMA-IOA-CHMA/MMA Block Copolymer
The B-block of the polymer isolated in Step 2 was converted to
poly-IOA by trans-esterification. The trans-esterification was
carried out by refluxing the polymer in isooctanol for about 10-12
hours in the presence of 10 mol % (based on TBA units only) of
para-toluenesulfonic acid. NMR testing confirmed the conversion of
TBA to IOA and that no trans-esterification of the CHMA or MMA had
occurred. The polymers produced are described in Table 1.
TABLE 1 B Block A Block Molecular Weight Molecular Example Polymer
Description and Ratio of CHMA/MMA Weight 1 CHMA/MMA-IOA- 8,000
180,000 CHMA/MMA 60/40 2 CHMA/MMA-IOA- 10,000 170,000 CHMA/MMA
60/40 3 CHMA/MMA-IOA- 13,000 170,000 CHMA/MMA 65/35 4 CHMA/MMA-IOA-
15,000 160,000 CHMA/MMA 57/43 5 CHMA/MMA-IOA- 21,000 170,000
CHMA/MMA 60/40
Examples 6-7
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 6-7 except that the ratio of CHMA/MMA in the A Block was
varied as shown in Table 2.
TABLE 2 B Block A Block Molecular Weight Molecular Example Polymer
Description and Ratio of CHMA/MMA Weight 6 CHMA/MMA-IOA- 10,000
170,000 CHMA/MMA 35/65 7 CHMA/MMA-IOA- 18,000 170,000 CHMA/MMA
15/85
Examples 8-9
A series of polymers of the ABA block copolymer type were prepared
with differing ratios of IBMA/MMA in the A blocks with a molecular
weight of about 8,000 and poly-IOA of about 70,000 molecular weight
in the B block. The preparation of each polymer was carried out
using atom transfer polymerization techniques in a 2 step
synthesis.
Step 1: Preparation of poly-isooctylacrylate Macro-initiator
In a glass vessel dried and purged with nitrogen was added toluene,
diethylmeso-2,5-dibromoadipate/CuCl difunctional initiator and
isooctyl acrylate monomer. The reaction was run at 85.degree. C.
for about 24 hours so the isooctylacrylate monomer conversion was
near 100%.
Step 2: Preparation of IBMA/MMA-IOA-IBMA/MMA Block Copolymer
To the difunctional poly-IOA initiator prepared in Step 1 was added
the IBMA and MMA monomers in the desired ratio, while keeping the
vessel inerted. Polymerization was allowed to proceed for about 24
hours at 85.degree. C. The reaction was then quenched by exposure
to oxygen and cooling. To remove most of the copper catalyst, the
sample is filtered through a short silica column. The polymer can
be recovered by precipitation in methanol or the solvent can be
removed by evaporation. The summary properties of the polymers are
shown in Table 3.
TABLE 3 B Block A Blocks Molecular Weight Molecular Example Polymer
Description and Ratio of IBMA/MMA Weight 8 IBMA/MMA-IOA- 8,000
70,000 IBMA/MMA 30/70 9 IBMA/MMA-IOA- 8,000 70,000 IBMA/MMA
70/30
Example 10
The same procedure used to prepare Examples 1-5 was used to prepare
Example 10 except that the molecular weight of the B Block was
about 210,000, the molecular weight of the A block was about 25,000
and the ratio of CHMA/MMA was 80/20.
Examples 11-25 and Comparative Examples C1-C3
Several of the polymer samples described above were combined with
tackifying resin. The block copolymer and tackifying resin amounts
are given in Table 4 (the parts by weight of tackifying resins were
added in to 100 parts by weight of block copolymer). The resulting
compositions were dissolved in toluene to form 30-40 weight percent
solids solutions and knife coated on PET film. The coatings were
dried in an oven at 70.degree. C. for 15 minutes and conditioned in
a constant temperature (25 degrees Celsius) and humidity 20 room
(50% relative humidity) for 24 hours before testing. Adhesive
testing was carried out according to the test methods listed above
and the results are shown in Table 5. Additionally, comparative
adhesives were prepared and tested according to the same procedure.
Comparative Example C1 is a 95.5/4.5 IOA/AA copolymer with inherent
viscosity (measured in ethylacetate at 27.degree. C.) of about 1.6
dl/g. Comparative Example C2 is a 90/10 IOA/AA copolymer with
inherent viscosity (measured in ethylacetate at 27.degree. C.) of
about 1.85 dl/g. Comparative Example C3 was prepared by dissolving
100 parts by weight of Kraton D1107 at about 35% solids in toluene.
To this solution, 100 parts by weight of Wingtack Plus are added
and the mixture is allowed to agitate to form a homogenous solution
for coating. The results for adhesive testing is presented in Table
5.
TABLE 4 Polymer F105 F85 R1018 SP553 BLUE X Example Example (PHR)
(PHR) (PHR) (PHR) (PHR) 11 3 -- 81.8 18.2 -- -- 12 3 41 -- 9 -- --
13 3 -- 101 21.5 -- -- 14 5 79 -- -- -- 43.3 15 5 23.2 23.2 3.6 --
-- 16 5 32.4 -- 67.6 -- -- 17 5 -- -- -- 31.8 68.2 18 10 -- 86.5
35.7 -- -- 19 1 -- 95.5 35.7 -- -- 20 1 45.3 -- 4 -- -- 21 2 --
93.9 28.3 -- -- 22 2 44.1 -- 5.2 -- -- 23 4 -- 89.4 32.8 -- -- 24 4
41.3 -- 7.9 -- -- 25 5 -- 86.0 36.2 -- --
TABLE 5 180.degree. peel 180.degree. peel Shear Quick Polymer from
glass from PE Strength Stick Example Example (N/dm) (N/dm)
(minutes) (N/cm) 11 3 61.8 49.0 NM 1.91 12 3 46.2 48.6 NM 2.68 13 3
74.8 63.5 1,197 1.25 14 5 50.4 53.5 NM 0.61 15 5 49.4 45.1 2,748
3.31 16 5 38.1 19.0 265 2.15 17 5 50.0 21.9 10,000 2.62 18 10 85.3
63.5 19 3.68 19 1 65.4 51.9 29 3.73 20 1 43.2 38.6 241 2.50 21 2
68.5 40.9 328 3.63 22 2 46.8 26.5 6,200 3.17 23 4 56.3 48.7 868
4.13 24 4 33.7 32.2 465 2.94 25 5 57.1 25.2 1,065 2.49 C1 C1 20.6
11.8 81 1.67 C2 C2 45.5 3.3 382 1.26 C3 C3 54.7 27.4 10,000 2.52 NM
= Not Measured
Examples 26-27
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 26-27 except that in Example 26 isooctyl alcohol was used
in Step 3 and in Example 27 n-butanol was used in Step 3 to give B
blocks of poly-IOA or poly-NBA respectively. The polymers are
described in Table 6.
TABLE 6 A Block B Block Molecular Weight and Molecular Example
Polymer Description Ratio of CHMA/MMA Weight 26 CHMA/MMA-IOA-
21,000 190,000 CHMA/MMA 60/40 27 CHMA/MMA-NBA- 21,000 130,000
CHMA/MMA 60/40
Examples 28-30
Adhesive formulations were prepared from the polymers prepared in
Examples 26-27 as described for Examples 11-25 using the reagents
listed in Table 7. Adhesive testing was carried out using the test
methods described above and the results are shown in Table 8.
TABLE 7 Polymer F105 F85 R1018 SP553 BLUE X Example Example (PHR)
(PHR) (PHR) (PHR) (PHR) 28 26 87.5 -- 34.8 -- -- 29 26 -- -- --
35.0 87.2 30 27 -- -- -- 21.3 100.2
TABLE 8 180.degree. peel 180.degree. peel Shear Quick Polymer from
glass from PE Strength Stick Example Example (N/dm) (N/dm)
(minutes) (N/cm) 28 26 65.6 51.4 169 2.94 29 26 53.6 43.8 2 2.90 30
27 33.9 37.2 1 2.30
Examples 31-32 and Comparative Examples C4-C5
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 31-32 with the ratio of CHMA/MMA in the A Block and the
identity and molecular of the B Block as shown in Table 9.
Comparative Examples C4 and C5 were prepared similarly only with
only MMA (Comp.Ex. C4) and CHMA (Comp. Ex. C5) as the A Block
monomer.
TABLE 9 A Block Molecular Weight, B Block Molecular Example
Monomers and Monomer Ratio Weight and Monomer C4 4,000, MMA 100
40,000, IOA 31 4,000, MMA/CHMA 67/33 40,000, IOA 32 4,000, MMA/CHMA
33/67 40,000, IOA C5 4,000, CHMA 100 40,000, IOA
Examples 33-34 and Comparative Examples C6-C7
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 33-34 with the ratio of CHMA/MMA in the A Block and the
identity and molecular weight of the B Block as shown in Table 10.
Comparative Examples C6 and C7 were prepared similarly only with
only MMA or CHMA as the A Block monomer.
TABLE 10 A Block Molecular Weight, B Block Molecular Example
Monomers and Monomer Ratio Weight and Monomer C6 10,000, MMA 100
100,000, IOA 33 10,000, MMA/CHMA 70/30 100,000, IOA 34 10,000,
MMA/CHMA 30/70 100,000, IOA C7 10,000, CHMA 100 100,000, IOA
Examples 35-37 and Comparative Examples C8-C9
A series of polymers of the ABA block copolymer type were prepared
with differing ratios of CHMA/MMA in the A blocks with a molecular
weight of about 8,160 and poly-2-EHA of about 120,000 molecular
weight in the B block. The preparation of each polymer was carried
out using atom transfer radical polymerization technique in a 2
step synthesis.
Step 1: Preparation of Poly-2-ethylhexyl Acrylate
Macro-initiator
In a glass vessel dried and purged with nitrogen was added
2-ethylhexyl acrylate as the monomer,
diethylmeso-2,5-dibromoadipate as the difunctional initiator, and
CuBr complexed by tris[2-(dimethylamino)ethyl]amine as the
catalyst. The reaction was run at 60.degree. C. for about 24 hours
so the 2-ethylhexyl acrylate monomer conversion was near 100%.
Step 2: Preparation of CHMA/MMA-EHA-CHMA/MMA Block Copolymer
The difunctional poly-2-EHA macro-initiator prepared in Step 1 was
diluted with butyl acetate. Then, while keeping the vessel inerted,
a solution of the catalyst (CuCl complexed by
1,1,4,7,10,10-hexamethyltriethylenetetramine), dissolved in methyl
methacrylate and cyclohexyl methacrylate in the desired ratio,
together with a small amount of methyl ethyl ketone, was added.
Polymerization was allowed to proceed for about 24 hours at
90.degree. C. The reaction was then quenched by exposure to oxygen
and cooling. To remove most of the copper catalyst, the sample is
filtered through a short silica column. The polymer can be
recovered by precipitation in methanol or the solvent can be
removed by evaporation. The summary properties of the polymers are
shown in Table 11. Comparative Examples C8 and C9 were prepared
similarly only with only MMA (Comp. Ex. C8) and CHMA (Comp. Ex. C9)
as the A Block monomer.
TABLE 11 A Block Molecular Weight, B Block Molecular Example
Monomers and Monomer Ratio Weight and Monomer C8 8,160, MMA 100
120,000, EHA 35 8,160, MMA/CHMA 75/25 120,000, EHA 36 8,160,
MMA/CHMA 50/50 120,000, EHA 37 8,160, MMA/CHMA 25/75 120,000, EHA
C9 8,160, CHMA 100 120,000, EHA
Examples 38-39
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 38-39 with the ratio of CHMA/MMA in the A Block and the
identity and molecular weight of the B Block as shown in Table
12.
TABLE 12 A Block Molecular Weight, B Block Molecular Example
Monomers and Monomer Ratio Weight and Monomer 38 21,000, MMA/CHMA
40/60 190,000, IOA 39 21,000, MMA/CHMA 40/60 190,000, BA
Examples 40-41
The same procedure used to prepare Examples 1-5 was used to prepare
Examples 40-41 with the ratio of CHMA/Styrene in the A Block and
the identity and molecular weight of the B Block as shown in Table
13.
TABLE 13 A Block Molecular Weight, B Block Molecular Example
Monomers and Monomer Ratio Weight and Monomer 40 7,400,
Styrene/CHMA 55/45 120,000, IOA 41 8700, Styrene/CHMA 30/70
120,000, IOA
Examples 42-43
The same procedure used to prepare Examples 8-9 was used to prepare
Examples 42-43 with the ratio of IBMA/MMA in the A Block and the
identity and molecular weight of the B Block as shown in Table
14.
TABLE 14 A Block Molecular Weight, B Block Molecular Weight Example
Monomers and Monomer Ratio and Monomer 42 8,000, MMA/IBMA 70/30
70,000, IOA 43 8,000, MMA/IBMA30/70 70,000, IOA
Example 44
Dynamical Mechanical Testing was carried out on some of the polymer
samples using the test method described above. The crossover
temperature was determined as the point where G' and G" curves
intersect or when Tangent delta=1 in the flow region of the
viscoelastic curve. The rubbery plateau range when determined and
the crossover temperature are presented in Table 15.
TABLE 15 B Block A Block Molecular Molecular Rubbery Cross-over
Polymer Weight, Monomers Weight and Plateau Temperature Example
Example and Ratio Monomer (.degree. C.) (.degree. C.) 44A C4 4,000
- MMA 100 40,000, IOA 10-125 170 44B 31 4,000, MMA/CHMA 40,000, IOA
10-80 100 67/33 44C 32 4,000, MMA/CHMA 40,000, IOA 10-35 50 33/67
44D C5 4,000, CHMA 100 40,000, IOA none 40 44E C6 10,000, MMA 100
100,000, IOA NA >240 44F 33 10,000, MMA/CHMA 100,000, IOA 10-160
220 70/30 44G 34 10,000, MMA/CHMA 100,000, IOA 10-160 190 30/70 44H
C7 10,000, CHMA 100 100,000, IOA 20-70 90 44I C8 12,000, MMA 100
120,000, EHA 0-100 170 44J 35 12,000, MMA/CHMA 120,000, EHA 0-80
104 75/25 44K 36 12,000, MMA/CHMA 120,000, EHA 0-50 71 50/50 44L 37
12,000, MMA/CHMA 120,000, EHA 0-25 48 25/75 44M C9 12,000, CHMA 100
120,000, EHA None 36 44N 38 21,000, MMA/CHMA 190,000, IOA 10-130
160 40/60 44O 39 21,000, MMA/CHMA 190,000, BA 30-80 100 40/60 44P
40 7400, Styrene/CHMA 120,000, IOA 170 55/45 44Q 41 8700,
Styrene/CHMA 120,000, IOA 130 30/70 44R 42 8,000, MMA/IBMA 70,000,
IOA 10-110 130 70/30 44S 43 8,000, MMA/CHMA 70,000, IOA None NA
30/70
* * * * *